CVE-2026-33436: Stirling-PDF: Reflected XSS through crafted filename in file upload functionality

Severity: medium (CVSS 6.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-04-17 · updated 2026-10-26
Weakness: CWE-20

Description

Stirling-PDF is a locally hosted web application that facilitates various operations on PDF files. In versions prior to 2.0.0, file upload endpoints render user-supplied filenames directly into HTML using unsafe methods like innerHTML without sanitization. An attacker can craft a file with a malicious filename containing JavaScript that executes in the uploading user's browser context, resulting in reflected XSS. The issue affects numerous upload endpoints across the application. The issue has been fixed in version 2.0.0.

Affected products

Stirling-Tools Stirling-PDF: before 2.0.0 — fixed in 2.0.0

How to fix

Upgrade to a fixed version: Stirling-Tools Stirling-PDF 2.0.0. Check the vendor advisory for mitigations.

References

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